Summary

The application of nanotechnology in the oil industry has become a useful approach in oil production. The main objective of this study is to investigate the effect of nanofluids on the recovery of heavy crude oil compared with waterflooding. The nanofluids are prepared by the addition of pure and mixed nanoparticles--silicon oxide, aluminum oxide, nickel oxide, and titanium oxide--at different concentrations to the formation water. The prepared nanofluids were screened to determine the suitable type for the heavy oil and rock samples subjected to the study. The effect of nanofluids on the interfacial tension and viscosity of emulsion were also investigated. Nanofluid-flooding tests were performed on a heavy-oil sample of 17.45 API by use of Berea sandstone core samples with average air permeability of 184 md, liquid permeability of 60 md, and porosity of 20%. After selection of the optimum type of nanofluid, additional tests were performed including effect on asphaltene precipitation by use of a flow-assurance system. Results from the experiments show that the aluminum oxide nanofluid at concentration of 0.05 wt% reduced the emulsion viscosity by 25%. The mixed nanofluid of silicon and aluminum oxides at 0.05 wt% has shown the highest incremental oil recovery among the other nanofluids. It is expected to be the best type of chemical flooding because of its performance in reservoir condition (high pressure, temperature, and water salinity) and its capability to oppose asphaltene precipitation.

The application of nanotechnology in the oil industry has become a useful approach in oil production. The main objective of this study is to investigate the effects of nanofluids on the recovery of heavy crude oil compared to water flooding. The nanofluids are prepared by the addition of pure and mixed nanoparticles; Silicon oxide, Aluminum oxide, Nickel oxide, and Titanium oxide at different concentrations to the saline water. The prepared nanofluids were screened to determine the suitable type for the heavy oil and rock samples subjected to the study. The effects of nanofluids on the interfacial tension and emulsion viscosity were also investigated. Nanofluids flooding tests were performed on heavy oil sample of 17.45 API using Berea Sandstone core samples with an average air permeability of 184 mD, a liquid permeability of 60 mD, and a porosity of 20%. After selecting the recommended type of nanofluid, additional tests were performed including the effects on asphaltene precipitation using a flow assurance system. The experimental results show that, the Aluminum oxide nanofluid at a concentration of 0.05 wt.% reduced the emulsion viscosity by 25%. The mixed nanofluid of Silicon and Aluminum oxide at 0.05 wt.% showed the highest incremental oil recovery among the other nanofluids. This nanofluid is expected to be the best type of chemical flooding due to its performance under reservoir condition (high pressure, temperature, and water salinity) and its capability to oppose asphaltene precipitation.

Introduction

The oil industry is facing challenges in terms of materials and safe environmental operations, as world energy consumption is expected to increase in the upcoming years. It is important to use the improved oil recovery (IOR) methods since large amounts of the original oil in place are left after the production through primary recovery.1 Currently, studies of the effects of nanotechnology in the oil industry are significantly increasing due to the ability of nanotechnology to improve some of the important factors that have an optimistic effect on the oil recovery.2-7 Despite positive achievements with nanoparticles studies, some studies are still under laboratory and research development. However, other studies can be implemented in the oil and gas industry to overcome issues caused by conventional recovery mechanisms such as adsorption, chemical, and thermal degradation issues and working in cruel temperature and salinityconditions.8-10 Additionally, nanoparticles can be used to increase oil recovery, improve water disposition, break emulsions, change the hydrophilic and hydrophobic behavior of water flood applications, and maintain the reservoir pressure above the bubble point.11

Enhanced oil recovery (EOR) processes are mainly classified into three major categories which are gas miscible flooding, thermal processes, and chemical flooding. Miscible flooding is a general term for injection processes that introduce miscible gases into the reservoir. However, poor reservoir volumetric sweep efficiency is the major problem associated with this type of flooding.12 Thermal processes provide a driving force by adding heat to the reservoir which increases oil production by reducing oil viscosity. This method includes steam flooding and cyclic steam injection. The main disadvantage of this method is the heat loss during the injection process which limits its applicability for deep reservoirs.13 Chemical flooding is performed by the addition of chemicals (polymer, surfactant, or alkaline fluid) to increase oil recovery mainly by decreasing interfacial tension (IFT) or increasing water wettability.14 These chemicals are not applicable at high water salinity or high water hardness, and there might be some damage or distortion at high reservoir temperatures.15 Therefore, new technologies are necessary to establish an ideal EOR method that should lead to an appropriate spread of fluid deep inside the formation, a minimum chemical adsorption onto the reservoir rock, fluids and/or chemicals that can withstand high water salinity and perform well under high reservoir temperature, and a high reduction of IFT between the injected fluid and oil.16

Viscosity and Density are important physical parameter of crude oil, closely related with the whole processes of production and transportation, and are very essential properties to the process design and petroleum industries simulation. As viscosity increases, a conventional measurement becomes progressively less accurate and more difficult to obtain. According to the literature survey, most published correlations that are used to predict density and viscosity of heavy crude oil are limited to certain temperatures, API values, and viscosity ranges. The objective of present work is to propose accurate models that can successfully predict two important fluid properties, viscosity and density covering a wide range of temperatures, API, and viscosities. Viscosity and density of more than 30 heavy oil samples of different API gravities collected from different oilfield were measured at temperature range 15oC to 160oC (60oF to 320oF), and the results were used to ensure the capability of proposed and published correlations to predict the experimental viscosity and density data. The proposed correlation can be summarized in two stages. The first step was to predict the heavy oil density from API and temperature for different crudes. The predicted values of the densities were used in the second step to develop the viscosity correlation model. A comparison of the predicted and actual viscosities data, concluded that the proposed model has successfully predict all data with average relative errors of less than 12% and with the correlation coefficient R2 of 0.97, and 0.92 at normal and high temperatures respectively. Meanwhile, the results of most of the available models has an average relative error above 40%, with R2 values between 0.19 to 0.95. These comparisons were made as a quality control to confirm the reliability of the proposed model to predict density and viscosity values of heavy crudes when compared with other models.

Thermal recovery methods have the objective of accelerating hydrocarbon recovery by raising the temperature of the formation and reducing hydrocarbon viscosities. Thermal recovery involves several well-known processes such as steam injection, in situ combustion, steam assisted gravity drainage (SAGD), and a more recent technique that consists of heating the reservoir with electrical energy. The most common thermal method is steam injection. However, some difficulties occurs with steam injection includes; water availability, the cost of water vaporization process, and how to keep steam temperature above the condensation temperature at reservoir conditions. Also it is limited to relatively shallow, thick, permeable, and homogenous sand reservoirs that are located onshore.

In this project three unconventional thermal approaches were developed in laboratory scale to improve the recovery of heavy oil. Those methods are; electrical resistant electrodes, electromagnetic inductors, and microwaves. Designing and experimenting were prepared using low cost material to achieve the success of the new approaches. In the electrical resistance approach, a potential difference was applied between two electrodes; one act as anode and the other one as a cathode. A sufficient heat has been introduced between the electrodes, which improved the oil recovery by adding a maximum of 21% additional recovery to the primary recovery. For the electromagnetic induction, a coil has been wrapped around a core through which the introduced heat was transmitted to the fluid inside and hence increasing the oil recovery by a maximum of 34%. As for the microwave method, microwaves were applied on the core to vibrate water molecules. These microwaves were created and applied by using normal microwave oven, where the waves were transmitted from the source, and reflected inside an isolating body to prevent any wave leakage. The molecules movement resulted in heat generation and thus a reduction in the oil viscosity. The conducted test revealed an increase of 30% in the oil recovery which varies according to the operating power. Finally, economical comparison between the proposed methods was conducted. The three methods were compared by combining recovery and power consumption. Average power consumption per unit production for electromagnetic induction, Electrical Resistance, and microwave were 39, 2570, and 3.775 watt.hr/cc, respectively. The comparison revealed that the Microwave Heating is the most economical choice followed by electromagnetic induction and finally the electrical resistance heating.

The escalating oil demand and maturity of most of the giant oil fields in the world, especially in the Middle East, the techniques for improving oil recovery have became more feasible and essential. Kuwait long term strategy is to increase oil production to meet marked demand. Currently, miscible gas injection is considered for enhancing oil production from Kuwaiti oil reservoirs. A key parameter for assessing the applicability of gas injection for a given reservoir is the minimum miscibility pressure (MMP). In this paper various miscibility experiments for planning gas injection projects in major producing fields in Kuwait are discussed. These experiments include swelling tests, slim-tube tests, and core flooding studies. These tests are useful tool for screening of the potential reservoirs for improving their future oil production and for developing suitable EOS for planning gas injection projects of the chosen fields.